If the specified validator address is in your keyring:
bandd keys show <your-wallet> --bech val -a
Otherwise
bandd query staking validators --chain-id odin-testnet-heimdall --node https://node.testnet.odinprotocol.io/nidavellir
will return all the system validators, and you can get odinvaloper... address there
bandd tx slashing unjail \
--from=<operator-key-name> \
--chain-id odin-testnet-heimdall \
--node https://node.testnet.odinprotocol.io/nidavellir